Absorbent materials and absorbent articles are known in the art and are known to have a wide variety of uses. Examples of such absorbent materials and absorbent articles include, for example, personal care products, such as disposable diapers and training pants; feminine hygiene products, such as sanitary napkins and tampons; incontinent care products, such as pads and undergarments; health care items such as, for example, bandages. Other absorbent materials and absorbent articles include wipers, absorbent mats and soakers. Because the fluids these products are designed to absorb have different properties, it is often difficult to provide an absorbent material which will efficiently absorb a wide variety of fluids. Therefore, various treatments for improving the absorbency, fluid distribution and fluid retention of absorbent materials and absorbent articles have been developed.
Highly viscous fluids are often difficult to absorb into absorbent products. For example, in feminine hygiene products, the viscoelastic properties of menses often make it challenging to absorb and distribute within the feminine hygiene products. The viscosity and/or elastic components of such fluids tend to impose requirements for absorption and/or distribution within the absorbent structure of the absorbent product. These requirements are often inconsistent with the best performance with respect to other components of the fluid that are less viscous or elastic with the result that a compromise in overall performance usually is required. For example, the pore and capillary sizes in an ideal material for absorbing and distributing less viscoelastic components are different from those that work best for the more viscoelastic components. Menses is a viscoelastic fluid composed of blood (primarily red blood cells and plasma), cervical mucus and/or tissue fragments. Mucin is found in virtually all menses samples. Mucin is a large linear glycoprotein having molecular weights up to 20 million or more. In combination with water and salts, mucin is a principal component of mucus, including cervical mucus. Mucin, with its large linear molecules, is believed to form networks in solution, giving rise to viscoelastic properties.
Mucin causes many challenges in menses absorbent products. Mucin in menses reduces intake of the menses fluid through the cover or body facing surface of an absorbent product. In addition, mucin tends to hamper fluid distribution in the absorbent article due to its highly viscoelastic and stringy nature. It is believed that mucin forms a three-dimensional network on the surface of the absorbent product, thereby blocking the intake ability of the absorbent product. When additional insults of menses come into contact with the three-dimensional network on the surface of the absorbent product, the additional insults may flow over the three-dimensional network, thereby causing the absorbent product to leak. Further, if the mucin component does penetrate the surface of the absorbent product, the mucin may clog the pores of the underlying absorbent layers, thereby causing a local saturation (most, if not all, of the pores in an area being filled to capacity) of the absorbent layer and/or the intake layer. The local saturation could cause leakage or prevent further distribution of the menses within the absorbent article or individual layers which may be present in an absorbent article in the x, y and z directions.
In addition to menses, there are other viscous materials which are difficult to absorb, including, for example, feces (or bowel movements), exudates from wounds, mucus, fluids containing food and plant proteins. It has been suggested in the art, as described in U.S. Pat. No. 6,060,636 to Yahiaoui et al. which is hereby incorporated by reference, to use viscoelastant agents such as alkyl polyglycosides having 8-10 carbon atoms in the alkyl chain to reduce the viscosity of viscous fluids. Other viscoelastant agents suggested by Yahiaoui et al. include bovine lipid extract surfactant (Survanta, Ross Laboratories), a drug used to treat Acute Respiratory Distress Syndrome and Cystic Fibrosis, and enzymes such as papain or pepsin, which cleave protein structures. Some dextrans may also be used as viscoelastants. Dextrans are (α-1-6) polymers of glucose with chain-like structures and molecular weights up to, for example, 2,000,000 daltons produced from sucrose, often by bacterial action.
Enzymes are known in the art to break-up or cleave proteins such as those found in mucin. However, enzymes can cause skin sensitization. Therefore, placing enzymes directly on an absorbent article may make the absorbent article unusable for some potential users, due to the sensitization the enzymes may cause. Further, the enzymes may migrate from the absorbent article onto the user, such as onto the user's skin. Hence, the use of enzymes in absorbent materials and absorbent articles have been avoided.
There is a need in the art for an absorbent system which will effectively absorb and retain viscous materials, which can use the advantages of enzymes with a reduced risk of sensitization to the user on the absorbent product.